1. Field of the Invention
The present invention relates, in general, to valves for controlling fluid flow into and out of containers and, specifically, to valves and fittings for controlling fluid flow into and out of gas sample containers.
2. Description of the Art
Expandable, sealed containers or bags are employed for collecting and temporarily storing gas emissions from various sources such as air, smokestack discharge, effluent and motor vehicles. The containers are then connected to suitable test equipment, such as a gas chromatograph, for example, to test the gas stored in such container.
The expandable containers include a fitting sealingly mounted in each container which can alternately be connected to the gas source to receive gas emissions therefrom or to the test equipment for analyzing a previously collected gas sample stored within the container. The fitting directs the gas into the container for storage as well as enabling the stored gas contents to be evacuated from the container for subsequent analysis. The fitting and the sealed container are typically made of a chemically inert material, such as a fluorinated carbon plastic, i.e., plastic sold under the registered trademarks TEFLON, KYNAR, and/or TEDLAR.
Frequently minute amounts of gas, i.e., 5 to 10 ml, are withdrawn from the container stored in a gas sample container. The valves or fittings previously used with motor vehicle gas emission sample containers are movable between fully closed and fully opened positions and discharge large quantities of gas from the containers when opened. This prohibits any subsequent testing of the gas remaining in the container since it is impossible to discharge only a minute quantity from the container.
U.S. Pat. No. 4,915,356 discloses a valve for controlling fluid flow into and out of a container through an elastomeric flow control element which is disposed in the fluid flow path between the inlet and outlet of the valve. When the flow control element is moved to the flow blocking position between the inlet and outlet of the valve, a syringe can be inserted through the element to withdraw a minute quantity of gas from the container attached to the valve.
While this valve provides a means for sampling minute quantities of gas within a sealed container without discharging large quantities of gas from the container, the elastomeric flow control element is located in the main fluid flow path and movement of the flow control element by a surrounding collar opens and closes the valve. Such repeated opening and closing operations can cause wear of the flow control element which could lead to loss of its sealing characteristics.
Another prior art valve manufactured by Welsh Fluorocarbon and used with sealed containers is shown in FIG. 10. This valve includes a body 1 having a through bore extending therethrough. An annular collar 2 has a centrally located, longitudinally extending, hollow tubular portion which is press fit into one end of the through bore in the body 1. A pierceable septum 3 is mounted between one end of the body 1 and the annular collar 2 in contact with a flexible sheet 4 which forms one side wall of a sealed container. An aperture is formed in the septum 3, the annular collar 2, and the flexible sheet 4, with the tubular portion of the annular collar 2 extending through the aperture in the flexible sheet 4.
An elongated stem 5 is slidably mounted in the bore of the body 1 and has a longitudinally extending bore 6 which terminates in an outlet port spaced from one end of the stem 5. An O-ring 7 is mounted on an annular disk slidably disposed about one end of the stem 5. A metallic washer is also disposed about the stem 5 and is located adjacent to the annular disk supporting the O-ring 7. A set screw 8 threadingly extends through the body and is engageable with the stem 5 to lock the stem 5 in the closed position shown in FIG. 10. In this position, the O-ring 7 sealingly engages an internal shoulder formed in the bore of the body 1 and closes off fluid flow through the bore 6 in the stem 5. The bore 6 in the stem 5 is in turn connected to an external conduit, not shown, for fluid flow through the valve to the sealed container as well as to evacuate the sealed container of fluid through the body 1 and stem 5.
To open the valve to fluid flow to and from the sealed container, the set screw 8 is unthreaded and the stem 5 is pushed into the body 1 until an enlarged end portion of the stem 5 engages an edge formed on the annular collar 2 surrounding the centrally located aperture therein. In this position, the outlet of the bore 6 in the stem 5 is open to the internal bore within the body 1 for the flow of fluid through the stem 6 into or out of the sealed container on which the valve is mounted.
A small diameter bore 9A is formed in one end of the body 1 and is aligned with a bore 9B formed in the annular collar 2. A syringe may be extended into the bore 9A, through the septum 3 and the bore 9B into the interior of the sealed container to withdraw minute quantities of gas stored within the sealed container. When the syringe is withdrawn, the septum 3, which is formed of a self-healing material, closes the opening formed by the syringe to seal off the interior chamber within the sealed container.
While this valve permits the withdrawal of minute quantities of gas from the sealed container on which the valve is mounted, it relies on a threaded set screw to lock the valve in the closed position. Due to the formation of the components of this valve from plastic, repeated opening and closing of the set screw results in wear of the engagement point between the set screw and the stem which, over time, can result in less than secure locking of the stem which could permit slight movement of the stem from the closed position and thereby prevent the stem from completely sealing the bore in the body.
Further, due to the formation of the stem in a single diameter, the stem can only be connected to a single sized conduit or external fitting thereby limiting the valve to only a single size external connection. Further, steel pins, not shown, are forced through the aligned portions of the body 1 and the centrally located tubular portion of the annular collar 2 to fixedly join the annular collar 2 to the body 1. Since it is difficult to remove the pins from the body 1 and the annular collar 2 without destroying the valve, this valve can only be used in a single application on a particular sealed container. If it is necessary to remove the valve from the sealed container, the entire valve must be completely replaced.
Thus, it would be desirable to provide a valve for a sealed gas container which overcomes the deficiencies found in previously devised valves of the same type. It would also be desirable to provide a valve for a sealed gas container which is easy to open and close while still providing an expedient means to remove minute quantities of gas from or inject gas into a sealed container attached thereto without discharging large quantities of gas from the container. It would also be desirable to provide a valve having these features which can be easily mounted on a sealed gas sample container. It would also be desirable to provide such a valve which can easily be detached from the container for reuse of the valve and the container. It would also be desirable to provide such a valve which is capable of receiving different size fittings. Finally, it would be desirable to provide such a valve which has multiple ports for separate fluid flow paths to the container.